Since phosphazene compositions have excellent characteristics, they have been studied in various fields and suitably used in a wide variety of the fields. For example, they are proposed for various uses such as flame retardants for polymer materials, rubbers, lubricants, lithium ion batteries, solar batteries, fuel cells, non-combustible electrolytes, battery equipment, releasing agents, releasing films, rough surface forming materials, water repellants, and, besides, fertilizers, medicines such as anticancer medicines, aids inhibitors, and dental materials.
As to the flame retardants, conventional methods for flame retardation of flammable resins include those which comprise adding chlorine compounds, bromine compounds, antimony trioxide or the like to resins. However, these methods are not preferred from the point of view of environmental protection and toxicity, and improvement of flame retarding methods has been demanded. As alternatives to flame retardants devoid of chlorine, bromine and metal oxides; phosphorus-based flame retardants have been investigated. Hitherto, red phosphorus, phosphate esters, condensed phosphate esters, etc. have been used as the phosphorus-based flame retardants, but red phosphorus suffers from the problems in hydrolysis and corrosion of molds due to production of corrosive phosphoric acid. Phosphate esters and condensed phosphate esters have the problems that they must be added in large quantities because of their relatively low phosphorus concentration. This causes deterioration of mechanical properties and thermal properties and increases the cost owing to addition of them in a large quantities. Furthermore, in case they are added to resins, decrease of glass transition temperature of the resins is great and heat resistance thereof is deteriorated. In addition, when they are used for electric or electronic equipment, they are also inferior in resistance to hydrolysis.
On the other hand, phosphazene compounds are desirable because they are high in phosphorus content and relatively superior in heat resistance and resistance to hydrolysis and have excellent flame retardancy. Recently, some proposals have been made of methods for flame retardation of resin composition with phosphazene compounds. Examples of the proposals are: flame retardant resin compositions comprising a styrenic resin-containing thermoplastic resin composition; a phosphazene compound and a polyphenol compound as reported in JP-A-08-302124; and flame retardant epoxy compositions comprising an epoxy resin to which phenoxyphosphazene is added as reported in JP-A-10-259292. These proposals are effective from the viewpoint of imparting flame retardancy. However, when the compositions are to be used in fields which require characteristics such as resistance to hydrolysis and excellent stability of electric characteristics, the above proposals are not satisfactory. Japanese Patent No. 3053617 discloses a phosphazene composition which is lower in volatile content after being heated for 2 hours over a boiling water bath (i.e., JIS-K2246). However, the patent makes no mention of the effect which the content of the volatile components exerts on flame retardancy, resistance to hydrolysis and stability of electric characteristics. The use of the phosphazene composition obtained by the above method is also not sufficient in resistance to hydrolysis and stability of electric characteristics.
As disclosed in the following, any effects of volatile components contained in phosphazene compositions found by the inventors cannot be learned from these conventional technologies. That is, proposals on flame retardancy, resistance to hydrolysis and stability of electric characteristics, taking into consideration the volatile components contained in the phosphazene compositions, cannot be inferred from the conventional technologies, and this technology has for the first time been accomplished by the present invention.